Q. What should I do about my moldy bathroom?A. It’s a safe bet that scientists, as a demographic, have among the nation’s lowest incidence of bathroom mold.“I squeegee after I shower,” said Tim Ryan, an associate professor of environmental health sciences who specializes in fungus research at Ohio University in Athens. “I don’t really have fungi problems. The key is to keep organic content down.” Right next to the yellow ducky.Dr. Ryan, like many of his colleagues, is aware that the air in his bathroom, and everywhere else, is filled with floating mold spores, and he takes pains not to provide a landing strip. Mold needs two things to grow: water and food. Eliminate either and you eliminate the mold problem.But in the bathroom, a room the British call the water closet for good reason, eliminating water isn’t viable.Cutting off food, though, is.Mold eats organic matter, meaning anything with particles that were once, or still are, alive: dirt, skin cells, cotton, cardboard, dust, hair, paper, wood.

That mold on your ceramic tile? It lives off dirt and soap, not the tile. Eliminating organic material from the bath is easy, Dr. Ryan said, because “the shower has almost no organic material.”“There might be soap scum and skin cells, but you can clean those,” he continued. “So I keep the shower stall as clean of scum and dirt as possible.”Modern Bedroom Furniture PhoenixAttacking existing mold is where those who aren’t scientists frequently go wrong. Wedding Chair Covers With BroochesFirst, an area two to three times the size of the visible mold must be cleaned, because mold has already spread beyond the area where it is seen.Audi Q7 Car Seat InstallationAnother key is the cleaning solution. A mix of 1 part bleach to 10 parts water is more effective than straight bleach, he said.

It should be mixed at cleaning, used promptly and not put on a shelf. Once food and water are eliminated, drain the tub after use and towel up any floor puddles. Mold-resistant paints are preferable, and if there is direct sunlight, leave the shade up, as some ultraviolet rays can kill spores.Abandon that beautiful fabric shower curtain, particularly if cotton, as mold eats it up (glass shower doors are preferable).Even wet towels pose a problem, Dr. Ryan said, so make sure they dry fully within 12 hours (a sign of appropriate ventilation).For those wondering why mold grows on ceilings, doors or other surfaces besides the bathing area, it’s because moisture escapes. Thomas Kenney, the vice president for engineering at the National Association of Home Builders in Washington, said the trick is to give the moist air a place to go. “You want to ventilate during the bathing process,” he said.This can be done by opening a window in the bathroom or nearby. Running a dehumidifier also helps, as does installing an exhaust fan through an exterior wall or ceiling vent in homes where mold is a serious problem.“

I would choose a model that’s quiet,” Mr. Kenney said. There are many to pick from, he noted, and they typically cost about $70. “You might look for a duty cycle timer, which automatically turns on the fan at regular intervals.”Paradoxically, advances in home building are responsible for some of the challenges. As Stephen Weeks, a principal at Boora Architects in Portland, Ore., said: “Houses built before around the 1970s breathe naturally because they’re drafty. In the 1980s we started building tighter houses, wrapping them on the outside with all sorts of papers and high-tech materials to keep water out. But what we were also doing is trapping water inside.”New energy-efficient homes often have nifty automatic ventilation systems that address this.For those who wonder about the difference between bathroom mold and basement mildew, Dr. Ryan has some final advice. They are “essentially the same thing,” he said. joints, especially those running through a hot attic,

create a moist environment duct joints with the special flexible mastic available at heating and cooling supply In warm environments, impermeable vinyl wallcoverings can trap moisture-laden air as it moves from the warm exterior to theMold degrades the drywall and adhesive behind the vinyl wallcovering. Use paint or apply wallcoverings with permeable paper backings that don’t trap moisture on exterior walls. When washing machines in a room without a floor drain overflow or hose connections burst, water with no point of exit will soak into adjacent carpet, drywall and Always provide a floor drain near theInstall an overflow pan directly under the machine or install a 1-in. lip at the doorway to contain overflows in main-level or second-story laundry Water-resistant drywall used as a tile backer quickly degrades once subjected to moisture. Install cement backer board, which will remain structurally sound even if repeatedly subjected to

Poorly ventilated bathrooms allow surface mold to grow. Install a bathroom fan (or at least, open a window) to exhaust moisture. Remove surface mildew by scrubbing the area with a 1/2 percent bleach solution. the area is dry, prime it with an alcohol-based, white pigmented shellac, such as Zinsser Bullseye, and use a paint Poorly constructed crawlspaces promote mildewBare earth floors transmit huge amounts of There are many regional differencesCover bare earth with 6-mil poly sheeting. Heat, cool and humidify the area the same as the rest of the house. Freshly cut firewood stored Humidifiers (especially reservoir-type central units and portable units) provide both a growth medium and a distribution system for mold and mildew. Clean and treat the reservoir often with an antimicrobial solution, available at The condensation pan directly under the coil of your central air conditioner can harbor mold.

Before each cooling season, clean the pan with a 1/2 percent bleach solution and make sure the continuous drain is working. Finished concrete basements that haven’t been thoroughly waterproofed from the outside are problematic. When moisture migrates through the earth and non-waterproofed concrete walls, it can get trapped behind vapor barriers, carpet, layers of insulation and drywall. Thoroughly waterproof the exterior of concrete walls before backfilling. Install 6 in. of gravel under concrete floors during construction to prevent moisture from wicking up through concrete floors and Yards that slope toward foundations invite water to enter basements and crawlspaces. Regrade yard surrounding house so it slopes away at a rate of 1 in. per foot. Improperly flashed or caulked windows (and those with large amounts of surface condensation) let moisture seep into the surrounding wood, drywall and insulation.